Ok, here's the dope:
0 rate=9%=u% 1000.00=a
1000 bucks deposited in savings account at year 0, at 9% compounded annually.
12% compounded annually will later be the rate, effective at a time k which will
result in a future value of 3000 bucks after 11 years.
For this to happen, k = 5.451118.....
If opening rate = u and opening deposit = a,
second rate = v , future value = b and number of years = n,
(v > u, b > a(1+u)^n)
what is k in terms of a,b,n,u,v?
Yep...general case formula:
k = LOG[(1 + u) / (1 + v)] / LOG[b / a / (1 + v)^n]